1. The Field of the Art
The present invention pertains to the field of the art of wind machines in general and in particular to the field of the wind turbine machines classified as either cross wind or vertical axis machines.
2. The Prior Art
Cross wind or vertical axis wind machines are generally known to be simpler to manufacture, whereas they moreover offer certain advantages when compared with wind machines of the horizontal type.
A first main inherent advantage of vertical axis wind machines is their ability to directly exploit the incoming wind independent of the direction at which it is blowing, without the assistance of orientation mechanisms of any type. This results to a lower manufacturing cost and a higher efficiency because of the simpler structure due to elimination of orientation mechanisms.
Another advantage exhibited by vertical axis wind machines is their ability to deliver the mechanical power produced at ground level, without employing complicated efficiency reducing mechanisms. Wind machines of the horizontal axis type would either necessitate complicated mechanisms such as bevel gears, elongated shafts, bearings or other transmission mechanisms or they would alternatively have to provide for mounting the electro-generator onto the wind mill tower, thereby loading the tower excessively and necessitating additional automation and wiring at a high level above the ground, which results in installation and maintenance difficulties. The elimination of such mechanisms in vertical axis wind machines renders a simple and cheaper construction, without the structural reinforcements otherwise necessary to support heavy machinery or mechanisms at certain heights, thereby leading to a further increase in the efficiency of the system.
Another advantage of vertical axis wind machines over the horizontal axis ones is their ability for a higher exploitation of the wind power, since their swept area in proportion to the ground occupied surface is by comparison larger.
Despite of their general superiority in comparison with horizontal axis wind machines, the vertical axis wind machines of the prior art also present certain drawbacks such as the relatively lower efficiency of the Savonius rotor and the additional inability of the Darrieus rotor machine to start by itself. The reason for the Savonius rotor exhibiting such a low efficiency is that the wind strikes on both sides of the rotor blades, i.e. the one following the wind direction and the other which counters it, thereby neutralizing part of the available wind force.
It is therefore the main object of the present invention to overcome the above drawbacks of vertical axis wind machines and provide a vertical axis wind machine, which will be capable of eliminating the counter acting impulse exerted by the wind on a certain portion of the rotor blades, whilst being capable of a maximum exploitation of wind power irrespective of the direction of the blowing wind, without necessitating any type of orientation mechanism, and furthermore providing self starting capabilities.
The above main object of the invention is accomplished by means of a wind turbine cross wind machine, which comprises an arrangement of guide vanes, circum-ferentially disposed around a centrally located rotor, these guide vanes being capable of maximally exploiting the wind, irrespective of the direction of its blowing, by forcing it to fall upon the rotor blades and positively assist in their direction of rotation without exerting any drag effect, which in the case of Savonius rotor is exerted by that portion of rotor blades rotating counter to the wind direction.